In most of the keywords i have chosen i have to increase quality or bid more to activate .. I would like to know if the amount needed to activate is calculated according to the number of competitors also ?
Yes, but there are a lot of factors that like the volume of search for that keyword. If a word is very competitive like for example "Web hosting" but the volume of searchs is very high the min bid is low. Other factor that has influency is your history CTR for this same keyword - if the CTR is very low the adWords system aks you to bid a high value to put your low CTR AD in the system again.